I have an 87 n/a that's having what seams like several independent problems and I'm having trouble figuring out the sources. There three issues it seams to having are:

-A shimmy in the steering wheel: usually not noticable unless slowing down, but gets quite strong when braking. This has been around for a month or two, and predates the other two problems.

-A vibration from the rear end: This only happens in 3rd and 4th gear at certain RPM's but is pretty significant. I originally suspected the wheel bearings, so when I was having my tires balanced I asked my mechanic to take a look at them. They told me that they tightened the real wheel bearings, and immediately afterwards the problem was almost (but not completely) resolved. Since then it has been steadily getting worse again.

-An improper camber in the rear wheels: There should be none, but after replacing the rear shocks I find that there is often a camber to the wheels. It changes frequently, is always negative (or neutral), and is not always the same on both sides.

I don't have very much experience dealing with this area of the car, so I'm not sure what I'm looking for. Any input in appreciated.

Any shimmy you feel in the steering wheel is most likely in the front not rear.

If rear bearings were tightened up to get better and they were worn, then of course they will wear more again to do the same and faster the second time.

The shimmy in the wheel as stated is in the front, and it's most likely brake rotors that are warped, this is why you feel it when braking, harder braking at higher speeds will make for a worse vibration.

The rear wheel bearings should not be able to be tightened, they are not tapered bearings. If they tightened the nut on the stub axle, which requires disconnecting the CV shaft, then the issue was that the stub axle was improperly installed. If this is the case then the stub axle may be damaged but hopefully just the bearings. They are a PITA to replace.

Rear camber is not adjustable. These cars use a variation of the semi trailing arm setup that dates back to the 510. As the suspension compresses you get more negative camber and more toe in. The springs were pretty soft to begin with but they can sag overtime making this issue worse. In addition there are 2 bushings on each trailing arm which could have deteriorated leading to excess movement of the arm, also a PITA to replace. Additionally the crossmember that these trailing arms attach to, attach to the body by way of a single bushing at either side, which is located right where the T top drain tubes come out, shortening the life of these bushings. Generally these make for a loose feeling at the rear fo the car, pretty easy to check wiht the car on a lift, even bigger PITA to replace.

Camber issue can be corrected with new springs. When the springs sag the tops of the tires tip inward. Very common in Z31s but new springs are fortunately pretty cheap.

So problems get bad when you get it up to speed? The rubber on these cars go bad so maybe you can try and inspect the bushings. As far as the steering, nissans are pretty reliable but their serpentine belts often wear and you might be having problems with steering due to this (assuming your PS fluid is topped off(.

Random quote of the day: I swear a nother teenager cuts me off and wants to race I'll toss a grenade in his/her path

Update in case anyone reads through this with similar problems:
All of the stated issues have been resolved. The shimmy in the wheel was a combination of old rotors and loose wheel bearings. The vibration in the rest of the car came from the same parts reaching resonance at certain speeds. The camber in the wheels was fixed completely with new rear springs. Thanks to everyone who picked in with help.